How much flash power does a softbox cost, and why was my fill flash underexposed outdoors?
Asked 3/15/2015
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2 answers
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I was shooting a backlit beach portrait at sunset with a Nikon D3200 and an SB-700 used as fill flash. Because the camera does not support high-speed sync, I used an ND filter to keep my shutter speed at or below flash sync while exposing for the bright background.
When I added a small softbox to the on-camera flash, the subject became much darker than shots made without the softbox, even with positive flash exposure compensation. Without the softbox the light was too harsh.
How many stops of light loss should I expect from a softbox or front diffuser? Do different softboxes and diffusion panels vary in transmission or color, and is there any rule of thumb for planning flash power loss outdoors?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
3
The problem you had is that your flash was at it's maximum output. No amount of flash exposure compensation will fix that.
For maximum flash effectiveness you want your shutter speed at exactly the maximum sync speed even if it does support HSS.
If that's still not bright enough at maximum flash power output, then you have options:
- Move the flash closer to the subject.
- Use more powerful lighting. An SB-910 for example.
- Remove any internal baffles in your softbox.
- Don't use the softbox at all.
- Shoot nearer sunrise or sunset when the sunlight isn't so bright.
http://neilvn.com/tangents/controlling-bright-daylight-with-direct-off-camera-flash/
Originally by user38805. Source · Licensed CC BY-SA 4.0
user38805
10y ago
0
Generated from our catalog & community — verify before relying on it.
A softbox or diffuser does reduce flash output, but there isn’t a single fixed EV loss that applies to all modifiers. Light loss depends on the specific softbox, its diffusion material, whether it has internal baffles, and how it’s mounted relative to the flash head. Different front diffusers can also vary in transmission, and potentially color slightly.
In your case, the main issue was likely that the SB-700 was already at or near full power. Once a flash is maxed out, adding positive flash compensation won’t make it brighter. The softbox then pushed it beyond what the flash could deliver.
Outdoors in bright conditions, the practical fixes are:
- stay at your maximum normal sync speed
- move the flash closer to the subject
- remove internal diffusion if possible
- use a more powerful flash/light
- skip the softbox if you need every bit of output
- shoot when ambient light is lower
If you want to know the exact loss of a given modifier, test it with a light meter or by direct comparison. That’s the only reliable way to budget the stop loss.
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AI11y ago
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